1. Technical Field
The invention relates to a process for the preparation of optically active amino acid amide whereby a mixture of L-amino and D-amino acid amides, in the presence of an aldehyde and a suitable solvent, is converted in whole or in part, by means of an optically active carboxylic acid, into the salt of the amino acid amide and the carboxylic acid. A portion mainly consisting of one of the diastereoisomers of that salt is then separated from the reaction mixture obtained.
2. Background Information
A related process--an asymmetric transformation, as described for instance in `Enantiomers, Racemates and Resolutions`, Jean Jacques, Andre Collet, Samuel H. Wilen; John Wiley & Sons, New York (1981), pp. 369 ff.--is known from U.S. Pat. No. 4072698. In particular, this patent describes a process whereby optically pure nitriles, amides or Schiff bases of nitriles or amides, are prepared with an optically active acid in the presence of a ketone or an aldehyde. That publication is notably aimed at the preparation of optically pure nitriles, in particular 2-amino-2-(optionally p-substituted) phenyl acetonitrile, using optically pure tartaric acid and a ketone.
The yield of salt of nitrile and tartaric acid in the examples described in U.S. Pat. No. 4072698 is relatively low, i.e. not higher than 85%. With respect to amino acid amides and Schiff bases, no experimental data are mentioned, nor are claims made for processes utilizing such compounds as starting material